JPH07133823A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE:To increase dynamic pressure in the thrust direction, to rotate a rotor in a stable state, to increase rigidity, to restrain whirling, to restrain abrasion of the end surface of the rotor and to restrain deflection of the rotor in the thrust direction. CONSTITUTION:This is furnished with a cylindrical rotor 1, a thrust wear plate 8 to support an end surface 2 of the cylindrical rotor 1 with dynamic pressure and an energizing means 4 to energize the cylindrical rotor 1 in the direction of the thrust wear plate 8. As the large diametrical end surface of the cylindrical rotor 1 is supported, peripheral speed of the end surface 2 is high and the dynamic pressure is also high. As the cylindrical rotor 1 is energized in the direction of the thrust wear plate 8, it is possible to restrain deflection of the cylindrical rotor 1 in the thrust direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device. More specifically, the present invention relates to a dynamic pressure bearing device that supports the end surface of a rotating body with a thrust receiving plate under dynamic pressure.

[0002]

2. Description of the Related Art Conventionally, as a dynamic pressure bearing device for supporting a rotating body in a thrust direction, there has been known a device for supporting an end surface 102 of a rotating shaft 101 in a thrust direction by a thrust receiving plate 103 as shown in FIG. Has been. Rotating shaft 101
A fluid 104 for generating a dynamic pressure is interposed between the end surface 102 and the thrust receiving plate 103. Fluid 1
As 04, liquid such as lubricating oil and magnetic fluid, or gas such as air is used.

[0003]

However, in a motor in which the diameter of the rotary shaft 101 cannot be increased so much, the rotary shaft 1
Since the end surface 102 of 01 has a small diameter, the peripheral speed of the end surface 102 of the rotating shaft 101 is small, and only a small dynamic pressure is generated. Further, in the structure as shown in FIG. 3, the thrust load is caused by the own weight of the rotor, so that the rotating shaft 10
When 1 has a small diameter, the thrust load also becomes light and the fluctuation in the thrust direction becomes large, which becomes a problem when it is used in something like a hard disk drive. In addition, when the end surface 102 of the rotating shaft 101 has a small diameter, the end surface 1
There is a problem that the degree of wear of No. 02 is large and affects the durability of the bearing device. Furthermore, when the rotating shaft 101 has a small diameter, the radial bearing rigidity also becomes small, the rotation of the rotating shaft 101 becomes unstable, and whirling is likely to occur.

According to the present invention, the dynamic pressure generated in the thrust direction is increased without changing the size of the bearing device itself, the fluctuation in the thrust direction of the rotor is suppressed, and the wear of the end face of the rotor is reduced. An object is to provide a dynamic pressure bearing device having excellent durability. The second aspect of the present invention is to provide a hydrodynamic bearing device in which the radial bearing rigidity is increased and whirling is suppressed without changing the size of the bearing device itself, and the rotating body rotates stably. To aim.

[0005]

In order to achieve such an object, a dynamic pressure bearing device of the present invention comprises a cylindrical rotary member and a thrust receiving plate for supporting the end face of the cylindrical rotary member by utilizing dynamic pressure. And a biasing means for biasing the tubular rotating body toward the thrust receiving plate.

Further, the urging means in the dynamic pressure bearing device of the present invention comprises a magnet provided on the thrust receiving plate, and urges the cylindrical rotating body to the thrust receiving plate by attracting the cylindrical rotating body. I am trying.

Further, in the dynamic pressure bearing device of the present invention, the magnetic fluid is sealed by forming the magnetic path of the biasing means.

[0008]

Therefore, since the tubular rotating body is always urged toward the thrust receiving plate by the urging means, the cylindrical rotating body is applied with a thrust load larger than the thrust load due to its own weight. Fluctuation in the thrust direction is suppressed. Moreover, since this rotating body is tubular,
A bearing member and a fixed shaft supporting the bearing member can be installed inside thereof, and a large dynamic pressure in the thrust direction can be generated on the outermost diameter side where the peripheral speed of the bearing device is high.

When the biasing means is composed of a magnet provided on the thrust receiving plate, the cylindrical rotating body is attracted to the thrust receiving plate by the attraction force and is formed between the biasing means and the cylindrical rotating body. The magnetic fluid used as the lubricating fluid is attracted and held by the magnetic force by the closed magnetic circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows the principle of the dynamic pressure bearing device of the present invention. This dynamic pressure bearing device includes a cylindrical rotating body 1, a thrust receiving plate 8 facing the end surface 2 of the cylindrical rotating body 1, and a biasing force for biasing the cylindrical rotating body 1 toward the thrust receiving plate 8. It has at least means 4 and is configured to generate a dynamic pressure by the lubricating fluid 7 between the end surface 2 of the cylindrical rotating body 1 and the thrust receiving plate 8. In the case of the present embodiment, the cylindrical rotating body 1 is rotatably supported by the fixed member and the bearing member arranged by utilizing the space inside thereof. That is, the cylindrical rotating body 1
A fixed shaft 5 as a fixed member for supporting the cylindrical rotating body 1 is installed inward of the above, and bearing members 6 and 6 are attached to the fixed shaft 5 to form a bearing. A magnetic fluid (hereinafter referred to as magnetic fluid 7) is filled as the lubricating fluid 7 between the radial bearing members 6 and 6 and the inner peripheral surface of the cylindrical rotating body 1. Here, the tubular rotating body 1 and the thrust receiving plate 8 are made of a magnetic material. Further, in the hydrodynamic bearing device of this embodiment, the annular magnet 4 is adopted as the urging means for urging the tubular rotating body 1 toward the thrust receiving plate 8. The magnet 4 is magnetized in the axial direction, and is arranged around the cylindrical rotating body 1 so as to be in contact with the thrust receiving plate 8. Further, in the case of the present embodiment, a magnetic permeable body collar 22 made of a magnetically permeable material is provided on the magnetic pole side of the magnet 4 which is not in contact with the thrust receiving plate 8. The magnetic permeable body collar 22 is press-fitted and fixed to, for example, a seal body 23 that surrounds the cylindrical rotating body 1 and encloses the magnetic fluid 7. Therefore, between the cylindrical rotating body 1 made of a magnetically permeable material and the thrust receiving plate 8, the magnet 4 → the magnetically permeable body collar 2 is provided.
A closed magnetic circuit F that flows from 2 → cylindrical rotator 1 → thrust receiving plate 8 is formed, and magnetic forces that try to attract each other are generated.

According to the dynamic pressure bearing device constructed as described above, the cylindrical rotary member 1 generates a large dynamic pressure between the cylindrical rotary member 1 and the thrust receiving plate 8 at the end face 2 having a large diameter and a high peripheral speed, and is stable. It rotates in the state of doing. Moreover, the cylindrical rotating body 1 is constantly attracted in the direction of the thrust receiving plate 8 by the magnet 4 as the urging means, the thrust load of the cylindrical rotating body 1 is increased, and the fluctuation of the cylindrical rotating body 1 in the thrust direction is reduced. To be done. In addition, the closed magnetic path F formed by the magnet 4 causes the cylindrical rotary body 1 to move from between the thrust receiving plate 8 and the end face 2 of the cylindrical rotary body 1 between the magnetically permeable collar 22 and the cylindrical rotary body 1. Magnetic fluid leaking out 7
Are retained and are confined in the gap between the cylindrical rotating body 1 and the magnet 4. Accordingly, the magnetic fluid 7 is sealed, and at the same time, the magnetic fluid 7 can be replenished between the end surface 2 of the cylindrical rotating body 1 and the thrust receiving plate 8. Further, since the magnetic fluid 7 is held between the thrust receiving plate 8 and the end surface 2 of the cylindrical rotating body 1 due to the formation of the closed magnetic path F, the dynamic pressure increases. Furthermore, since the large-diameter end surface 2 of the tubular rotating body 1 slides on the thrust receiving plate 8, the degree of wear of the end surface 2 of the tubular rotating body 1 is reduced. Further, since the cylindrical rotating body 1 has a large diameter, the radial bearing rigidity is large and the whirling is suppressed. Further, in this embodiment, since the radial bearing members 6 and 6 are arranged inside the cylindrical rotating body 1, the diameter of the fixed shaft 5 does not have to be large. On the other hand, even if the diameter of the fixed shaft 5 is increased, a sufficient dynamic pressure can be expected by reducing the wall thickness of the tubular rotary body 1.

As described above, a dynamic pressure bearing device capable of generating a large dynamic pressure, suppressing stable whirling, and suppressing swing in the thrust direction is, for example, a motor for a hard disk drive (HDD). It is suitable for motors that require precise rotation without shake.

FIG. 2 shows an example in which the dynamic pressure bearing device of the present invention is applied to a spindle motor for a hard disk drive. Here, in FIG. 2, only the right half from the center of the motor is shown, but the left half is symmetrical with the right half, and is not shown.

In this spindle motor, a rotor hub 9 is rotatably supported by a dynamic pressure bearing device using a magnetic fluid as a lubricating fluid. That is, this spindle motor
A hub 9 is press-fitted and fixed to the outer periphery of a cylindrical rotary body 1 that constitutes a rotary body of a dynamic pressure bearing device, and a fixed shaft 5 that constitutes a fixed body is supported by a frame 3. A rotor magnet 10 is fixed to the inner circumference of the hub 9, and a stator coil 11 is fixed to the outer circumference of the frame 3 facing the hub 9. The rotor magnet 10 and the stator coil 11 constitute a motor. An annular magnet 12 magnetized in the axial direction is fitted to the fixed shaft 5.
The annular radial bearing members 6, 6 made of a magnetically permeable material are press-fitted and fixed to the fixed shaft 5 in contact with both magnetic pole end faces. Further, magnetic seals 13 and 14 are provided on the inner peripheral surface of the tubular rotating body 1. The magnetic fluid 7 is filled in the gaps between the tubular rotating body 1, the radial bearing members 6 and 6, the magnet 12, and the fixed shaft 5.

Here, the tubular rotating body 1 and the radial bearing members 6, 6 are made of a magnetically permeable material, and the fixed shaft 5 is made of a non-magnetic material. Therefore, the magnetic fluid 7 is adsorbed and held between the outer peripheral surfaces of the radial bearing members 6 and 6 and the inner peripheral surface of the tubular rotating body 1 by the magnet 12.

The first magnetic seal 13 is in contact with the end surface of one of the bearing members 6 and is in contact with the end surface of the magnet 15 and an axially magnetized annular magnet 15 press-fitted and fixed to the fixed shaft 5. It is composed of an annular seal plate 16 as a magnetic pole piece that is press-fitted and fixed to the fixed shaft 5, and a seal plate 17 provided on the inner peripheral surface of the cylindrical rotary body 1 so as to face the seal plate 16. Therefore, the magnetic fluid 7 is adsorbed and held between the seal plates 16 and 17.

Further, the second magnetic seal 14 is an axially magnetized magnet 19 which is press-fitted and fixed to the inner peripheral surface of the cylindrical rotary member 1.
And a pair of annular seal plates 20, 20 as magnetic pole pieces that are in contact with both magnetic pole end surfaces of the magnet 19 and are press-fitted and fixed to the inner peripheral surface of the cylindrical rotating body 1. Therefore,
The magnetic fluid 7 is adsorbed and held between the seal plates 20, 20. An annular blocking plate 21 for preventing magnetic fluid leakage is provided on the open side of the second magnetic seal 14 by being press-fitted into the fixed shaft 5.

The thrust receiving plate 8 is made of a ring of magnetically permeable material and is embedded in the aluminum frame 3 for mounting the motor. And, around the thrust receiving plate 8,
The cylindrical seal body 23 formed of an elastic body has the cylindrical rotary body 1
Is provided so as to surround the outer periphery of the. This seal 23
At the time of assembling the bearing, the lip of the upper end opening is utilized to seal the magnetic fluid with the cylindrical rotating body 1. Further, an annular magnet 4 as a biasing means is arranged on the thrust receiving plate 8. The hole 24 for injecting the magnetic fluid is used for the magnetic fluid 7.
Is filled with the adhesive 25 or the like after the injection. Also,
A media hard disk (not shown) is fixed to the hub 9.

In the spindle motor configured as described above, the magnet 4 on the stator side attracts and holds the cylindrical rotating body 1 supporting the hub 9 toward the thrust receiving plate 8, and the cylindrical rotating body 1
Since the shake of the medium in the thrust direction is suppressed, it is possible to prevent a track shift or the like due to the shake of the medium in the thrust direction. Moreover, since the magnetic fluid 7 is prevented from flowing out to the stator coil 11 side by the magnetic fluid 7 being attracted and held by the magnet 4, the magnetic fluid 7 adheres to the stator coil, the rotor magnet, or the like to provide support for the motor function, The magnetic fluid 7 does not stain the medium. . As described above, since the shake in the thrust direction can be prevented and the magnetic fluid can be held by the single magnet 4, it is advantageous in terms of cost.

The above embodiment is one example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, the radial bearing members 6, 6
Is fixed to the fixed shaft 5, but the radial bearing members 6, 6 are fixed to the inner peripheral surface of the tubular rotating body 1 so that the inner peripheral surfaces of the radial bearing members 6, 6 slide with the fixed shaft 5. Alternatively, the radial bearing members 6, 6 may be arranged further on the outer periphery of the cylindrical rotating body 1.

In the above-described embodiment, the magnet 4 is used as the urging means for urging the cylindrical rotating body 1 toward the thrust receiving plate 8.
However, a spring or the like may be used. Further, as the lubricating fluid, the example in which the magnetic fluid 7 is mainly used has been described,
There is no particular limitation to this, and lubricating oil may be used, or a fluid different from the radial bearing portion may be adopted between the thrust receiving plate 8 and the end surface of the tubular rotating body 1. When a magnetic fluid is not used as the lubricating fluid, it is sufficient that at least the portion attracted by the magnet 4 is made of a magnetic material even if the entire tubular rotating body 1 is not made of a magnetic material. . Further, when a lubricating liquid such as magnetic fluid 7 is interposed between the cylindrical rotating body 1 and the thrust receiving plate 8 as in this embodiment, the thrust receiving plate 8 has a groove for generating dynamic pressure. Dynamic pressure is generated without forming
When a dynamic pressure is generated in the thrust direction using a gas such as air, it is necessary to form a groove for generating the dynamic pressure in the thrust receiving plate 8.

[0023]

As is apparent from the above description, the dynamic pressure bearing device of the present invention includes a cylindrical rotating body, and a thrust receiving plate for supporting the end surface of the cylindrical rotating body by a dynamic pressure of a lubricating fluid. Since the cylindrical rotating body is provided with an urging means for urging the rotating body toward the thrust receiving plate, and the dynamic pressure is generated in the thrust direction at the end surface of the cylindrical rotating body having a large diameter and a large peripheral speed, the bearing is used. Even if the device itself is not made large, a large dynamic pressure is generated and stable rotation occurs, and the cylindrical rotating body is constantly urged in the direction of the thrust receiving plate by the urging means to increase the thrust load, resulting in a cylindrical rotation. Fluctuations in the thrust direction of the body are reduced. Moreover, since the end surface of the cylindrical rotating body has a large diameter, the degree of wear of the end surface of the rotating shaft is small. Further, since the tubular rotating body has a large diameter, the radial bearing rigidity is large, and whirling around is suppressed.

Further, in the dynamic pressure bearing device of the present invention, when the biasing means is composed of the magnet provided on the thrust receiving plate, the cylindrical rotary member is thrust by magnetic attraction with a simple structure in which only the magnet is provided. When the magnetic fluid is used as the lubricating fluid, the magnetic fluid can be attracted and held between the end surface of the cylindrical rotary member and the thrust receiving plate to increase the dynamic pressure. Moreover, since the magnetic fluid is sealed by forming the magnetic path, the magnetic fluid that leaks out between the end face of the cylindrical rotating body and the thrust receiving plate to the outside of the cylindrical rotating body is retained, and the cylindrical rotating body and the magnet are separated from each other. It is possible to replenish the magnetic fluid between the end face of the cylindrical rotating body and the thrust receiving plate at the same time as being confined in the gap between them.

[Brief description of drawings]

FIG. 1 is a drawing showing the principle of a dynamic pressure bearing device of the present invention,
(A) is a longitudinal sectional view and (B) is an enlarged view of a main part.

FIG. 2 is a vertical cross-sectional view showing the right half from the center of an embodiment in which the dynamic pressure bearing device of the present invention is applied to a motor for a hard disk drive.

FIG. 3 is an explanatory diagram of a conventional thrust dynamic pressure bearing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical rotating body 2 End surface of cylindrical rotating body 4 Energizing means 7 Magnetic fluid (fluid for generating dynamic pressure) 8 Thrust receiving plate

Claims (3)

[Claims] 1. A cylindrical rotating body, a thrust receiving plate that supports the end surface of the cylindrical rotating body by utilizing dynamic pressure, and a biasing means that biases the cylindrical rotating body toward the thrust receiving plate. And a dynamic pressure bearing device. 2. The urging means comprises a magnet provided on a thrust receiving plate, and urges the cylindrical rotating body toward the thrust receiving plate by attracting the cylindrical rotating body. The dynamic pressure bearing device according to claim 1. 3. The hydrodynamic bearing device according to claim 1, wherein the magnetic fluid is sealed by forming a magnetic path of the urging means.